Magnetostrictive vibrator



C. ll, 1932. G W` PIECE 1,882,393

MAGNETOSTRICTIVE VIBRATO Original Filed March 23. 1928 jig. 1.

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Patented Oct. 11, 1932 UNITED STATES Pra-NT essie MAGNETOSTRICTIVEVIBRATOR Uriginal application led Harel). 23, 1928, Serial No. 264,222.Divided and this application iiled August 9,

` 1932. Serial No. 628,043.

The present invention relates to magnetostrictive vibrators. The presentapplication is a division of application Serial N o. 264,222, led March23, 1928,.and a continuation in part of application Serial No; 158,452,filed January 3, 1927, which matured, on March 11, 1930, into LettersPatent No. 1,750,124.

A magnetostrictive lvibrator comprlses a magnetostrictive core disposedin an electromagnetic field, such as may be established by passing anelectric current through a field coil or windin The core may be in theform of a rod or tu e, or any other desired form. Any material havingsuitable properties may be used for the core, but the material shouldobviously be characterized by comparatively large magnetostrictiveeffects and comparatively low vibrational decrement.

The chief object of the present invention is to provide a new andimproved magnetostrictive vibrator.

Other objects will be explained hereinafter and will be particularlypointed out in the appended claims, it being understood that it isintended to set forth, by suitable expression in the claims, all thenovelty that the invention may possess.

The invention will be explained in greater detail in connection with theaccompanying 3o drawing, in which Fig. 1 is a diagrammatic view of amagnetostrictive vibrator embodying the present invention; and Fig. 2 isa similar View of a modication.

A magnetostrictive core is axially posia solenoid field coil or winding10, with clearance to permit free vibrations. The coil 10 is providedwith conductors 12 and 14 by which it may be connected, for simplicity,1n series with a source D of alternating electromotive force, such as analternating-current generator 16. A local battery 18 (shown in serieswith the source 16 and the winding 10) applies a steady magnetizing orpolarizing field to the core, over which the alternating ield producedby the generator 16 is superposed. Further details will be found in theabove-mentioned Letters Patent.

If the current or voltage 1s alternating, the

electromagnetic field created thereby will also values be alternating.The core 2 will, therefore, increase and decrease in length (let us say)many times a second. The core 2 will, in consequence, .vibratemechanically by magnetostriction about a nodal point at its centerperiod of vibration equal to the period of the alternating electromotiveforce. The

vmechanical damping of the rod, mounted as propertiesmay, of course, beused for theA vibrating body 2, but it should obviously be constitutedof material that is suitably magnetizable. The core may bein the form ofa simple rod or tube of the proper material, o."

it may have any other desired form, as stated f in the said LettersPatent No. 1,750,124; but to obtain the best results, depending upon thepurpose for which the apparatus is used, the core or tube should becharacterized b comparatively large magnetostrictive e fects andcomparat1vely low vibrational decrement. By filing the vibrator down, oradding to its mass by solder or plating, or` by adding Weights, ashereinafter described,

any desired frequency may readily be at' tained, either high or low. Thevibrator may have weights rigidly attached to the ends thereof, asillustrated in the .said Letters Patent, or the weights may beadjustable, as in the form of split collars 97, 98, which may be clampedin adjusted position by screws or the like 99. These expedientseffectively decrease the period of vibration to comparatively lowadjustable cobalt and steel, in proper proportions, have comparativelylarge magnetostriction.

In addition to one or more natural funda'- mental frequencies ofmechanical vibration, the core has also frequencies of vibration Alloyscontaining nickel, chromium,

determined by the operation of the core in halves, thirds, fourths,fifths and other overtones. There will usually, therefore, be more thanone specific frequency of magnetization at which the core Will resonateas above described. Such other modes of vibration may be produced byparticular methods of stimulating the vibrations, or by particular modesof clamping the body.

And, of course, it will be understood that the invention is notrestricted to the use of vibrators in the form of tuned rods or tunedtubes. As a further example, the tuned vibrator may be constituted of aplurality of small wires embedded as a unit in a highly elastic bindingmaterial, or attached together by solder or by welding in suitablespots, as at their centers or ends. A core of this character will reducehysteresis and eddy currents, which would act in a detrimental manner athigh frequencies.

At frequencies as high as 200,000 cycles per second, a solidnickel-steel, michronie, or chromium-steel 'rod is highly efficient evenwhen its diameter isl as large as` one inch, and though used inmagnetizing coils that have a clearance of more than 1A inch all aroundthe core. By diminishing this clearance and using cores of smallerdiameter and shorter lengths, the upper limit of frequency can begreatly raised, and then properly constructed comniinuted cores withelastic binding material will serve still further to raise the limit ofavailable frequencies.

It will be noted that when vibrating at its fundamental frequency, thetwo halves of the centrally supported core are driven by equal andoppositely acting forces, so as to communicate practically no motion tothe' clamp and its base. The apparatus is, therefore, free from one ofthe sources of trouble and irregularity of tuning forks, the periods ofvibration of which are affected by the table or other support on whichthey are placed.

So well does the present vibrator balance itself about a central pivot 6that the clamp, between which the core is shown centrally clamped in thesaid Letters Patent, may be dispensed with and a mere rest 6 take itsplace, upon which the core freely rests centrally. With this arrangementthe frequencies may be changed at will by merely pulling out one rod andreplacing it by another. The core may be otherwise supported also.

To persons skilled in the art many other applications and modificationsof the apparatus will occur, and no effort has here been made to beexhaustive.

vWhat is claimed is:

1. Apparatus of the character described comprising a support, amagnetostrictive vibrator freely supported thereon so that itvibratoibeing such that the current owing through the coil is subjectedto the reaction of the vibrator due to the magnetostrictive eiects.

2. Apparatus of the character described comprising a support, amagnetostrictive vibrator freely supported centrally thereon, and a coilcooperatively related to the v`1- brator, the relation between the coiland the vibrator being such that the current flowing through of thevibrator due to magnetostrictive effects, whereby the vibrator will becaused to vibrate symmetrically about its center. 3. A magnetostrictivevibrator comprising a magnetostrictive core, and a coil cooperativelyrelated to the vibrator, the relation between the coil and the vibratorbeing such that the current flowing through the coil is subjected to thereaction of the vibrator due to niagnetostrictive effects, a Weightattached to the vibrator, ing the weight.

In testimony whereof, I have hereunto subscribed my name.

GEORGE w. PIERCE'.

readily may be interchanged for another vibrator, and a coilcooperatively related to the vibrator, the relation between the coil andthe the coil is subjected to the reaction Y and means for adjusty los

